The native English speakers might find this confusing. But this is a big problem in startups around the world.
You start out with a core team from the same country. Let's say French, for example.
Naturally, you default to writing and documenting in French. All good so far.
But hopefully your startup will grow. You'll want more and better talent. And that talent won't be French. It'll be Spanish, German, Brazilian, American, Indian, or any other nationality. They won't speak French. And so they'll a company where they'll understand nothing. They'll have to keep a Google Translate tab permanently open.
Besides, it'll be much harder for the rest of your French speaking team to then switch back to English.
And don't think it's free game in DMs. You might have to share a private convo you had with one of your teammates. But it's in French. So what now? You'll have to rewrite the whole context again instead of just sending a printscreen.
Always default to English from the very beginning. It opens you to the best talent in the world.